Abstract
A 71-year-old man presented with a 2-month history of multiple itchy eruptions mainly on the back. Each eruption consisted of a small, oval, slightly pigmented, thin, flat area that was less than 1 centimeter in diameter framed by narrow, elevated skin. Histological examination diagnosed this case as annular lichen planus (LP). One of skin lesions in this case was immunohistochemically investigated using monoclonal antibodies against HLA-DR, ICAM-1, CD1a, CD4, CD8 and Foxp3. HLA-DR and ICAM-1 signals protruded into normal-looking peripheral epidermis beyond the marginal area where liquefaction degeneration of the epidermis was prominent with mild lymphocytic infiltration, but rapidly diminished in the inner area of the lesion. The number of Langerhans cells was increased in the infiltrated and marginal areas, but rapidly normalized in the inner area. Helper, cytotoxic and regulatory T cells adhering to the basal cells in the infiltrated and marginal areas were distributed away from the epidermis in the inner area. The increase in epidermal Langerhans cells in the infiltrated and marginal areas, and their rapid normalization in the inner area may have resulted from the temporary expression of HLA-DR and ICAM-1 molecules. The annular formation, namely the regression of lymphocytic infiltration and recovery of the epidermis in the inner area of annular LP, may be closely related to the loss of epidermal HLA-DR and ICAM-1 expression, which enhances the infiltration of Langerhans cells and lymphocytes.Skin Research, 17: 181-185, 2018
